Gear reducer having symmetrically disposed rotational shaft supports and method for making same

ABSTRACT

A gear reducer includes rotating assemblies intermeshing with one another to transfer power. The assemblies are supported at one of four locations disposed in mirror image locations. Two of the locations are on a longitudinal centerline of the gear reducer. The other two locations are offset from the centerline at equal distances from the first two locations. The locations are positioned to accommodate both single and multiple-stage gear reducer configurations. Bearing supports are machined in identical housing shell blanks to support the rotating assemblies.

BACKGROUND OF THE INVENTION

1. Field Of The Invention

The present invention relates generally to the field of gear reducers,such as machines designed with one or multiple reduction stages forsupport on an input or output hub or shaft. More particularly, theinvention relates to a gear reducer employing a mirror-image symmetricallayout of shaft and hub axes accommodating multiple differentcombinations of pinions and gears, as well as both single and multiplestages of reduction in a product family utilizing a reduced number ofdifferent original manufacturing parts.

2. Description Of The Related Art

Gear reducers of various types are ubiquitous in the field of industrialmechanical power transmission. Such gear reducers are typically employedto reduce the speed of a rotational input shaft to a desired level, andto, consequently, increase the torque applied to a load. Many differentdesigns for such products have been proposed and are presently in use.In one particular type of gear reducer, sometimes referred to as atorque arm, one or more gear reduction stages are formed in a housingwhich may be supported on a machine surface, or which may be supporteddirectly on an input or output shaft as an overhung load. To provide therange of gear reduction combinations and torque and speed ratings neededby systems design engineers, manufacturers typically offer a range ofsimilar products through a product family, varying in each both therating of the various components, the overall gear reduction ratio, thetorque characteristics, mounting configurations, and so forth.

Gear reducers of the type described above may be configured as single ormultiple-stage machines. In general, the overall gear reduction ratio ofthe machine is defined by the parameters of input pinions or gears,intermediate pinions and gears, and output gearing. In a single-stagereducer, the gear reduction ratio is defined by the configuration of theinput pinion and output gear which intermesh with one another. Inmultiple-stage machines, the overall gear reduction is the product ofthe individual reduction ratios of the successive stages.

A significant challenge in the design of gear reducers is the layout ofgearing and support shafts in a manner that will provide the desiredreduction ratio, while respecting mechanical tolerances, spaceconstraints, strength constraints, and so forth. In general, each inputand output shaft or hub must be rotationally supported by supportbearings and surfaces of the support housing that can withstand theanticipated loading. Intermediate shafts, supporting intermediate stagepinions and gearing, must be similarly supported by bearings foranticipated loads. Moreover, input and output shafts or hubs, andintermediate shafts must be appropriately spaced from one another toaccommodate the desired gearing, the gearing itself dictating specificcenter distances of the various rotational axes from one another.

Attempts have been made in the past to judiciously configure gearreducer layouts, particularly the positions of various rotational axes,to accommodate more than one specific gear reducer size or rating. Inparticular, proposals have been made to provide several rotational axesin a symmetrical triangular configuration. The triangular configuration,in theory, allows for gear reducer housings to be employed in bothsingle-stage and multiple-stage machines. However, in practice, thesedesigns have proven less than optimal, particularly in view of themechanical support and machine required by the different loadinganticipated for input and intermediate shafts. Moreover, it has beenfound that in designs incorporating rotational shaft axes laid out in anisosceles triangle configuration, spacing constraints between thevarious rotational axes do not permit the degree of design flexibilityin the gearing ratios that would be desired.

There remains a significant need, therefore, for an improved design forgear reducers which facilitates the selection of individual pinion andgear sets, both for single and multiple-stage machines. There is aparticular need for an improved technique for the layout of a gearreducer which allows housing components to be employed across a range ofreducer ratings, sizes, and numbers of stages.

SUMMARY OF THE INVENTION

The present invention provides a gear reducer system designed to respondto these needs. The novel gear reducer design of the present techniquemay be employed in both single-stage machines, and multiple-stagemachines, but is particularly well suited to use in a family of gearreducers that may include both single and multiple-stage units. Whilethe technique may be employed in various housing configurations, it isparticularly well suited to gear reducers designed to be support on aninput or output hub or shaft. The technique employs a series ofrotational shaft axes laid out in a mirror-image configuration. In apreferred embodiment, four rotational axis locations are provided. Thelocations include two which are positioned along a longitudinalcenterline of the gear reducer, and two additional axes positioned atmirror-image locations offset from the centerline. In the gear reduceritself, reduction stage shafts or hubs may be positioned about fewerthan all of the rotational axis locations. In particular, in asingle-stage gear reducer, a first rotational shaft or hub may bepositioned along the centerline of the machine, with an output hub orshaft similarly along the centerline. Alternatively, the input or outputhub or shaft may be positioned at one of the offset locations, with theother hub or shaft positioned along the centerline. In a two-stage gearreducer, input and output shafts may be positioned at the locationsalong the centerline with an intermediate shaft being positioned at anoffset location. Alternatively, the input or output shaft location andthat of the intermediate shaft may be reversed.

In general, the technique provides a gear reducer in which rotationalaxis supports are provided in a bilaterally symmetrical arrangement. Thearrangement includes symmetry about an axis extending through at leastone vertex of a quadrilateral. Center distances between the verticesalong the longitudinal axis, and center distances between the twocentral vertices and the bilaterally symmetrical offset vertices areselected to accommodate both single and multiple stage gear sets.Housing components, bearing components, machining operations,inventories, and other costly facets of the gear reducer design andmanufacturing operations may thereby be significantly reduced for asingle gear reducer, as well as across a family of gear reducers sharingcommon components.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 is a perspective view of a speed reducer including a housingconfigured in accordance with certain aspects of the present technique;

FIG. 2A is an elevational view of the speed reducer of FIG. 1,illustrating certain preferred features and geometries useful inconfiguring the housing shells or components;

FIG. 2B is a sectional view of the gear reducer of FIG. 2A taken alongline 2B—2B;

FIG. 2C is a sectional view of the gear reducer of FIG. 2A taken alongline 2C—2C;

FIG. 3A is an elevational view of another speed reducer, including asingle gear reduction stage, and incorporating a housing configured inaccordance with certain of the inventive techniques;

FIG. 3B is a sectional view of the housing of FIG. 3A, taken along line3B—3B;

FIG. 4 is an elevational view of a single half or shell of the gearreducer housing of the type shown in FIGS. 2A and 3A, illustratingfeatures of the original casting and machined surfaces;

FIG. 5 is an elevational view of an opposite housing half or shelldesigned to mate with the housing shell of FIG. 4;

FIG. 6 is a detailed representation of a preferred technique for formingapertures for fasteners used to secure the housing shells to one anotherin a position-tolerant manner;

FIG. 7 is a diagrammatical representation of a preferred lay out forrotating assembly or shaft positions in the housing designed to permitadditional flexibility in the use of the housing for different gearreduction ratios and different numbers of gear reduction stages; and

FIG. 8 is a series of elevational views of gear reducers includinghousings designed in accordance with the present technique, and showingvarious orientations permissible by virtue of the positioning oflubricant fill, drain, and level apertures in the housing.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Turning now to the drawings, and referring first to FIG. 1, a two-stagegear reducer, represented generally by the reference numeral 10, isillustrated as including an input shaft 12 which will be driven in afinal application, and which will transmit mechanical power to an outputhub 14 as described more fully below. It should be noted that whilereference is made in the present description to input and output shaftsand hubs, aspects of the present invention are not intended to belimited to any particular input or output configuration. In particular,input can be made into the gear reducer via an input hub configuration,or a shaft, with output from the gear reducer being made through a hubas illustrated, or via an output shaft. Similarly, while reference ismade herein to a gear reducer, the machinery described herein may beemployed for increasing speeds, where desired. In the illustratedembodiment, input shaft 12 is provided with a standard key 16 fortransmitting torque, while output hub 14 is provided with a taperlocking coupling system 18 and a key. Again, any suitable arrangementsmay be made for coupling the input and output components to othermachinery, including keyed shafts and hubs, splined shafts and hubs, andso forth.

Gear reducer 10 includes a housing 20 for supporting at least the inputand output rotating assemblies associated with shaft 12 and hub 14, aswell as other rotating assemblies used to transmit torque between thesecomponents. As illustrated in FIG. 1, housing 20 includes a fronthousing half or shell 22, and a rear housing half or shell 24. Asdescribed in greater detail below, the housing shells are configured asidentical structures, such that initial blanks or castings for theshells may be machined and assembled to form both the front and backshells. Each shell 22 and 24 of housing 20 includes an extending bodyportion 26 designed to enclose internal components of the gear reduceras described below.

Each shell 22 and 24 of housing 20 includes a series of supportstructures integrally formed therein for mechanically supportingrotating assemblies. These assemblies may include the input shaft 12,the output hub 14, as well as additional input or output assemblies, andintermediate rotating assemblies for transmitting torque in multiplestages. In the preferred embodiment illustrated, four support structuresare provided on each housing shell, including an input support 28, andoutput support 30, a first offset support 32, and a second offsetsupport 34. Again, the designations as input or output supports shouldnot be interpreted as limiting the applicability of the various supportlocations. Input or output rotating structures may be provided at anyone of the supports. The front and rear shells of housing 20 each aresurrounded by a partial or, in the preferred embodiment illustrated, acomplete peripheral flange 36 for facilitating assembly of the gearreducer. In particular, the shells are secured to one another with therotating assemblies positioned therein, via a series of fastener sets 38extending through the peripheral flanges. As noted below, theconfiguration of the gear reducer with the peripheral flange andfastener sets also facilitates mounting of the gear reducer. Inparticular, machine mounting flanges, support structures, and so forth(not shown) may include apertures which also receive certain of thefastener sets extending through the peripheral flanges of the gearreducer to support the gear reducer in given applications.

In the preferred embodiment illustrated, the gear reducer featuresenable the gear reducer to be configured in one of a number of ratings,depending upon the internal configuration of the gearing intermeshing todefine the gear ratio. Moreover, the gear reducer housing isparticularly well suited to both single-stage configurations as well asmultiple-stage units, both based upon the same identical housing shellcastings. As described below, in the illustrated embodiments, referencenumeral 10 generally refers to an exemplary two-stage gear reducer,while reference numeral 11 (see, e.g., FIGS. 3A and 3B) refers to asingle-stage gear reducer constructed of the same housing shells, orhousing shells designed with the features described herein.

To facilitate the use of components through a variety of gear reducersizes and ratings, and to enable identical components to be used forfront and back portions of the gear reducer, certain of the structuralfeatures of the housing and gear reducer are formed in mirror-imagelocations as best illustrated in FIG. 2A. As shown in FIG. 2A, the gearreducer housing 20 in which gear reducer 10 (or 11 as described below)is assembled, has a longitudinal centerline 40 about which thestructural features are provided in mirror-image locations. The firstand second rotating assembly supports 28 and 30 are provided on thelongitudinal centerline 40. The third and fourth rotating assemblysupports 32 and 34, offset from the centerline 40, are centered atidentical distances from the centerline, as indicated by referencenumerals 42 in FIG. 2A. As described below, this configuration enablessupports on a front shell of the housing to correspond exactly tolocations of mirror-image supports on the rear shell of the housing.That is, for the front shell illustrated in FIG. 2A, offset support 32will overlie offset support 34 of the rear housing shell, with offsetsupport 34 of the front housing shell overlying offset support 32 of therear shell. The internal configuration of these features, and the mannerin which they overlie one another will be described more fully below.

In addition to the mirror-image locations of the rotating assemblysupports, housing 20 includes a series of locations for the fastenersets 38 which are also disposed in mirror-image locations aboutcenterline 40. In particular, in the illustrated embodiment a series offastener set locations are provided at distances 44, 46 and 48identically offset from the centerline. Thus, when front and rearhousing shells are mated with one another, fastener set locations oneither side of the centerline will overlie one another.

Referring now more particularly to the internal configuration of thegear reducer illustrated in FIG. 2A, FIGS. 2B and 2C depict twodifferent torque-transfer paths through the rotating assembliessupported at the support locations described above. FIG. 2B illustratesshaft 12 extending through front housing shell 22 and rear housing shell24 in a presently preferred arrangement. As shown in FIG. 2B, fronthousing shell 22 and rear housing shell 24 are identical structures,each including a generally planar wall 50 formed integrally with aperipheral wall 52. Walls 50 and 52 of each housing shell, whenassembled in the product, enclose an internal cavity 54 in which thegearing, bearings, and other components of the gear reducer arepositioned.

At each rotating assembly support location, the housing shells areprovided with support structures which can be machined to receive asupport bearing assembly for the rotating assembly. In particular, asshown in FIG. 2B, supports 28, receiving shaft 12, and supporting theshaft in rotation, each include a bearing support 56 machined withinenlarged regions or ribs integrally formed in the casting or blank fromwhich the housing shells are machined. Similar bearing supports 58 and60 are formed in front housing shell 22 and rear housing shell 24,respectively, to support an intermediate rotating assembly. Again, dueto the mirror-image and identical structures of the front and rearhousing shell castings, when assembled in the gear reducer as shown inFIG. 2B, support 32 of the front housing shell 22 overlies support 34 ofthe rear housing shell 24. Within bearing supports 56, bearingassemblies 62 are provided for supporting shaft 12 in rotation.Similarly, bearing sets 64 are provided in bearing supports 58 and 60 ofthe front housing shell 22 and the rear housing shell 24, respectively.

Each rotating assembly of the gear reducer, supported at a correspondingsupport location, will generally include a rotating support member, suchas a shaft or hub, and gearing, such as a pinion or gear wheel affixedto the shaft or hub. In the embodiment illustrated in FIG. 2B, inputshaft 12 includes a pinion 66 which is formed integrally with the shaft.Alternatively, gearing or a pinion may be affixed to the shaft in asubsequent operation. Shaft 12 extends through apertures 68 and 70formed through front housing shell 22 and rear housing shell 24,respectively. At each location where the shaft extends through theshell, seal assemblies (not shown in FIG. 2B) may be provided forretaining lubricant within the gear reducer housing and preventing theingress of contaminants and fluids from outside the housing. A blind endof shaft 12, extending through aperture 70 and rear housing shell 24 iscovered by a sealed cover assembly 72. An intermediate rotating assemblyconsisting of a shaft 74 and gear 76 are supported by bearings 64. Thegear 76 of the intermediate rotating assembly meshes with pinion 66 ofshaft 12 to provide an initial or first stage gear reduction. Thesecomponents are again illustrated in FIG. 2C, along with the rotatingassembly associated with hub 14.

Referring to FIG. 2C, bearing supports 78 are formed at the location ofoutput support 30 of both front and rear housing shells 22 and 24.Again, by virtue of the mirror-image configuration of the gear reducerhousing, and the use of identical front and rear shell castings, thelocations of these supports overlie one another in the assembledproduct. Bearing sets 80 are supported within bearing supports 78, and,in turn, support hub 14 in rotation. An output gear 82 is secured to hub14 and rotates therewith, intermeshing with a pinion section 84 of shaft74. Pinion section 84, in the illustrated embodiment, is formedintegrally with shaft 74 adjacent to the location of gear 76 in theassembled product.

In the case of the multi-stage gear reducer 10, the structure describedabove provides integral support locations for the input, output, andintermediate rotating assemblies in locations which overlie one another.It should be noted, that not all of the integral supports formed withthe housing shells need be machined to receive bearing sets or rotatingassemblies. In particular, in the multi-stage gear reducer 10 shown inFIGS. 2A, 2B and 2C, the offset support 32 of the front shell half ismachined to receive a bearing set, as is the offset support 34 of therear shell. However, the offset support 34 of the front shell, and theoffset support 32 of the rear shell need not be machined if no rotatingassembly is to be supported therein. It should also be noted, that whileidentically sized and rated bearing sets may be provided on either sideof each rotating assembly, depending upon anticipated loading, bearingsets of different sizes or ratings may be provided. In particular, asshown in FIG. 2B, bearing sets 62 on either side of input shaft 12 havedifferent sizes and ratings in view of the anticipated loading of theshaft. Similarly, the bearing supports formed in each support structuremay be machined to different dimensions (e.g., diameters and depths) toaccommodate the bearing set to be supported therein.

FIGS. 3A and 3B illustrate a single-stage gear reducer 11 configured inaccordance with the foregoing techniques, but including only a pair ofrotating assemblies intermeshing with one another. In particular,housing 20 of single-stage gear reducer 11 may be configured identicallyto the housing illustrated in the foregoing figures and described above,with mirror-image rotating assembly supports, fastener set locations,and so forth about a centerline as shown in FIG. 2A. However, where asingle gear reduction is needed, only certain of the locations need bemachined and assembled to support rotating shafts or hubs and theirassociated gearing. In the embodiment illustrated in FIG. 3A and 3B, aninput shaft 86 is supported by supports 28 of front and rear housingshells 22 and 24, while an output hub 14 is supported at support 30 ofboth housing shells. Input shaft 86 which may be generally similar toinput shaft 12 described above, or differently configured depending uponthe intended application and ratings, will typically include a pinionsection 88 designed to intermesh with an output gear 90 supported on hub14. Other supports and components of the assemblies may be substantiallyidentical to those described above. Because no rotating assemblies areprovided for gear reductions between the input and output rotatingassemblies, integral structures provided at supports 32 and 34 of boththe front and rear housing shells need not be machined to receivesupport bearings.

As summarized above, the gear reducers constructed in accordance withthe present techniques facilitate assembly and support of variousrotating assemblies, and configuration of a wide variety of gear reducertypes and ratings by virtue of features of the gear reducer housing andits associated components. FIGS. 4 and 5 illustrate identical blanks forthe front and rear housing shells 22 and 24, respectively, showingcertain of these features. As noted above, each housing shell includes aperipheral flange 36 in which fastener sets are received to secure thehousing shells to one another. Within each housing shell, rotatingassembly supports 28, 30, 32 and 34 are integrally formed. While anysuitable material and process may be used to form the shellsincorporating the useful features herein, presently preferred materialsand techniques include metal alloys, such as iron or steel alloys castto integrally form certain of the features, and subsequently machined torefine those features needed in the assembled product.

Among the features machined in the housing shells, peripheral flange 36preferably includes a smooth, flat sealing surface 92 formed by amilling operation on the housing shell blank. Apertures 94 and 96 formedthrough the flange may be conveniently cast, or may be machined in asubsequent operation. However, in the preferred embodiment illustrated,the apertures are elongated, with certain of the apertures beingelongated in a generally horizontal direction as indicated at referencenumeral 94, and other apertures being elongated in a generallyhorizontal direction as indicated at reference numeral 96. As describedmore fully below, with reference to FIG. 6, the elongated aperturesfacilitate assembly and alignment of the mirror-image housing shells. Inaddition to apertures 94 and 96, peripheral flange 36 preferablyincludes a series of machine fixturing recesses 98, three such recessesbeing cast into the illustrated housing shell in the preferredembodiment.

As will be appreciated by those skilled in the art, typical machiningprocedures for complex castings such as those employed in gear reducerhousings, often require a series of machining fixtures, each designed toappropriately support and orient the casting in general purpose orspecifically designed machine tools. The fixtures themselves, and thefixturing operations, can lead to substantial costs in the manufacturingprocess. The provision of fixturing recesses 98 has been found togreatly reduce the need to refixture the housing shells for machining ofthe various features required for supporting the rotating assemblies andfor maintaining a sealed and lubricated interior space in the product.In particular, peripheral flange 36 is preferably cast with a desiredthickness, with fixturing recesses 98 being of a reduced thickness.Moreover, fixturing recesses 98 are preferably of a thickness smallerthan the final thickness of flange 36 following machining of the sealsurface 92. Thus, the housing shells may be secured by clamps (notshown) in a machine fixture at the locations of fixturing recesses 98,and subsequent machining operations, including the formation of sealsurface 92, may be carried out through the use of conventional machinetools without removing the shell blank from the support fixture. Wheredesigned, the support fixture may be configured for rotation about oneor more axis to facilitate access to and machining of the variousbearing supports, seal surfaces, threaded lubricant supports, and soforth as may be designed into the final product.

The rotating assembly supports integrally formed into the housing shellblanks are machined in accordance with the needs of the final productconfiguration. In particular, as shown in FIGS. 4 and 5, where an inputshaft is to be supported at supports 28, bearing supports 56 willtypically be machined to receive bearing sets as described above. Anaperture 68 or 70 may also be machined at the first support location asdescribed above. Similarly, a bearing support 78 is machined to supportthe output rotating assembly at support 30, with additional surfacesbeing machined, as desired, to support seal assemblies and so forth. Atoffset supports 32 and 34, additional bearing support surfaces 58 and 60are machined to support an intermediate rotating assembly. It should benoted that in the illustrated embodiment bearing support 60 in fronthousing shell 22 is not machined and that bearing support 58 in rearhousing shell 24 is not machined. Again, it should be noted that,although the housing shell blanks are identical prior to machining, thefunctional designations of the support locations are identified in FIGS.4 and 5, such that offset support 32 of front housing shell 22 willoverlie offset support 34 of rear housing shell 24 when housing shell ispositioned thereon, with offset support 34 of front housing shell 22overlying offset support 32 of rear housing shell 24.

As noted above, the apertures formed in the peripheral flange of thegear reducer housing are preferably configured to permit tolerance inthe alignment of the fastener apertures during assembly. In particular,where the apertures are cast in the blank for the gear reducer housingshells, such tolerance may be useful in permitting some degree of driftof the actual fastener position. FIG. 6 illustrates the generalconfiguration of these apertures in the preferred embodiment. Inparticular, each generally horizontally disposed aperture 96 has a majoraxis 100 and a minor axis 102. The aperture is extended along axis 100such that its dimension along this axis is greater than its dimensionalong axis 102. Conversely, generally vertically disposed apertures 94have a dimension extended along axis 102 with respect to theirdimensions along axis 100. Thus, when the housing shells are secured toone another for product assembly, some degree of tolerance or drift ofthe actual point of crossing of the apertures is permitted, whilemaintaining the desired fastener clearance as defined by the smaller ofthe axial dimensions of apertures 94 and 96 (the dimension of aperture96 along axis 102 and the dimension of aperture 94 along axis 100). Itshould be noted that the apertures need not be oriented along axes whichare aligned with or orthogonal to centerline 40 of the gear reducerhousing as in the illustrated embodiment. Rather, in general, the axesmay be rotated from the orientation illustrated and permit some degreeof tolerance in the location of the fasteners as described. Moreover,major and minor axes for each aperture may be angularly oriented withone another by angles other than 90 degrees and still permit some degreeof fastener location tolerance.

As noted above, the preferred embodiment of the gear reducer and gearreducer housing described above includes supports for rotationalassemblies positioned at mirror-image locations. FIG. 7 illustratesdiagrammatically an exemplary and preferred lay out for the rotationalaxes in the embodiments described above. As shown in FIG. 7, first andsecond of the rotational assembly supports, designated by referencenumerals 28 and 30, lie along a centerline 40 of the gear reducer andgear reducer housing. Additional third and fourth rotating assemblysupports 32 and 34 are provided at mirror-image offset locations fromthe centerline 40. In the diagrammatical representation of FIG. 7, thesupports for the rotating assemblies are provided at locations 106 and108 along the centerline 40, and at the offset locations 110 and 112 oneither side of the centerline. Moreover, locations 106 and 108 arespaced from one another by a distance DA, represented by referencenumeral 114 in FIG. 7. Location 106 is also spaced from locations 110and 112 by a distance DB, as denoted by reference numeral 116 in FIG. 7.Finally, location 110 is spaced from location 108 by a distance DC, asindicated by reference numeral 118 in FIG. 7 (location 112 beingsimilarly spaced from location 108).

The symmetrical disposition of the axis locations for the rotatingassemblies in the present technique permit considerable designflexibility and interchangeabilty of parts in the product and infamilies of products. In particular, in the foregoing arrangements,distance DA (114 in FIG. 7) is selected to accommodate the appropriatecenter distance for single-stage gear reducers such as gear reducer 11described above. Distances DB and DC (116 and 118 in FIG. 7) are thenselected to accommodate various configurations for first and secondstages of two-stage gear reducers. The symmetrical disposition oflocations 110 and 112 allow for the use of identical components on frontand rear sections of the final product, and particularly of housingshell blanks which are machined at appropriate locations to receiverotating assembly support bearings.

It should be noted that the axis layout of FIG. 7 may be modified orutilized in various way to obtain similar advantages throughout variousproduct configurations. For example, while in the presently preferredembodiment an input rotating assembly is positioned at location 106,with an output rotating assembly positioned at location 108, one or bothof these locations could be used for input or output, or input andoutput rotating assemblies could be positioned at either of locations110 or 112. Moreover, the particular spacing selected between therotating assembly axis locations will vary depending upon the gearingselected, the torque and power ratings of the gear reducers, the numberof different combinations of gearing within the gear reducers, and theneed to utilize similar or identical components between single andmultiple-stage gear reducers.

The use of a modular housing and assembly approach to the gear reducersdescribed above offers additional advantages as indicated in FIG. 8. Inparticular, the housings may be mounted in one of several differentorientations based upon the particular application and the machinesupport provided in the application. In a presently preferredconfiguration, at least one of the housing shells is provided with aseries of ports or threaded apertures for receiving lubricant, draininglubricant, and controlling lubricant level. As shown in FIG. 8, foursuch apertures are provided in the illustrated embodiment, includingapertures 120, 122, 124 and 126. FIG. 8 illustrates a series of fourdifferent exemplary positions in which the gear reducer may be oriented,with the apertures serving different purposes in each position. Thelocations of the apertures are preferably selected to accommodate thesedifferent functions.

The positions illustrated in FIG. 8 include a first position 128, asecond position 130, a third position 132, and a fourth position 134(moving from the uppermost image in a clockwise direction in FIG. 8). Ineach position, one of the apertures serves as a fluid fill port in whicha lubricating oil may be poured to provide lubrication of the rotatingassemblies. An additional port serves as a fluid level control port. Athird port serves in each position as a fluid drain port. In theembodiments illustrated in FIG. 8, each port is provided along a desiredfluid level as defined by the particular locations of the rotatingassembly supports. The function of the ports then depends upon theparticular orientation of the gear reducer adopted in the application.

In the specific embodiment illustrated in FIG. 8, a first fluid level136 is defined in orientation 128, with port 126 being located at thatlevel. Port 120 then serves as a fluid fill port and port 124 serves asa drain port. In orientation 130, a desired lubricant level 138 isdefined, and port 120 is positioned at that level. Port 122 then servesas a drain port, with port 126 serving as a fill port. In orientation132, a desired lubricant level 140 is defined, with port 122 beinglocated at that level, port 120 serving as a drain port, and port 124serving as a fill port. Finally, in orientation 134, a desired lubricantlevel 142 is defined, with port 124 being provided at that level, port122 serving as a fill port, and port 126 serving as a drain port. Itshould also be noted that ports 120, 122, 124 and 126 do not have to beon one housing shell 22 as shown. For example, ports 122 and 126 couldbe moved to shell 24 with the same function being provided. In thiscase, the ports could be moved axially along the gear case and serve asfill, drain and level holes when the reducer is mounted with the shaftaxes vertical and the input shaft extending either up or down as inpositions indicated by reference numerals 144 and 146 in FIG. 8,respectively. In this orientation with the input shaft extending up,port 124 is the fill port, port 126 is the drain port and port 120 isthe level port. In orientation input shaft extending down, port 126 isthe fill port, port 124 is the drain port and port 122 is the levelport.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

What is claimed is:
 1. A gear reducer comprising: a support housinghaving a central longitudinal axis and first, second, third and fourthrotational member supports, the first and second supports being disposedalong the central axis for supporting rotational members havingnon-coincident rotational axes and spaced from one another by a distanceDA, and the third and fourth supports disposed at mirror image locationson either side of the central axis, the third and fourth supports beingspaced from the first supports by a distance DB and from the secondsupports by a distance DC; a first rotational power transmissionassembly including first gearing, the first rotational powertransmission assembly supported by the first rotational member supports;and a second rotational power transmission assembly including secondgearing, the second rotational power transmission assembly supported bythe second, third or fourth supports, the first and second gearingintermeshing to transmit power therebetween.
 2. The gear reducer ofclaim 1, wherein the first rotational power transmission assemblyincludes an output hub and the first gearing includes an output gearsecured to the hub within the housing.
 3. The gear reducer of claim 1,wherein the second rotational power transmission assembly includes aninput shaft and the second gearing includes a pinion portion supportedwithin the housing.
 4. The gear reducer of claim 1, further comprising athird rotational power transmission assembly including third gearing,the third rotational power transmission assembly supported by thesecond, third or fourth supports, the third gearing intermeshing withthe second gearing to transmit power therebetween.
 5. The gear reducerof claim 4, wherein the third rotational power transmission assemblyincludes an input shaft and an input pinion, and wherein the secondrotational power transmission assembly includes an intermediate shaft,an intermediate gear intermeshing with the input pinion, and anintermediate pinion intermeshing with the first gearing.
 6. The gearreducer of claim 5, wherein the third rotational power transmissionassembly is supported along the housing axis by the second supports, andthe second rotational power transmission assembly is supported at anoffset position by the third supports.
 7. The gear reducer of claim 1,comprising bearing sets for supporting rotational assemblies, thebearing sets being provided only at those supports supporting arotational assembly.
 8. The gear reducer of claim 1, wherein thedistance DA is selected based upon a center distance for a single stagegear reducer configuration.
 9. The gear reducer of claim 1, wherein thedistances DB and DC are selected based upon center distances for firstand second stages of a two stage gear reducer configuration.
 10. A gearreducer comprising: a support housing having a central longitudinal axisand first, second, third and fourth rotational member supports, thefirst and second supports being disposed along the central axis andspaced from one another by a distance DA, and the third and fourthsupports disposed at mirror image locations on either side of thecentral axis, the third and fourth supports being spaced from the firstsupports by a distance DB and from the second supports by a distance DC;a first rotational power transmission assembly including first gearing,the first rotational power transmission assembly supported by the firstrotational member supports; and a second rotational power transmissionassembly including second gearing, the second rotational powertransmission assembly supported by the second, third or fourth supports,the first and second gearing intermeshing to transmit powertherebetween; wherein locations of the supports form a quadrilateralhaving internal angles less than 180 degrees.
 11. A gear reducercomprising: a housing comprising a pair housing shells having alongitudinal centerline and at least four support locations forrotational axes of rotating assemblies, first and second supportlocations being disposed along the centerline for supporting rotationalmembers having non-coincident rotational axes and spaced from oneanother by a distance DA, and third and fourth support locations beingdisposed at mirror image locations on either side of the central axis,the third and fourth support locations being spaced from the firstsupport location by a distance DB and from the second support locationby a distance DC; and at least two intermeshing rotating assemblies,each rotating assembly including a rotational shaft or hub and gearingrotational with the shaft or hub, each rotating assembly having arotational axis coincident with a respective support location axis, atleast one of the rotating assemblies being disposed at the first supportlocation.
 12. The gear reducer of claim 11, comprising two rotatingassemblies, wherein a first rotating assembly is disposed at the firstsupport location and a second rotating assembly is disposed at thesecond support location.
 13. The gear reducer of claim 11, comprisingthree rotating assemblies, wherein a first rotating assembly is disposedat the first support location, a second rotating assembly is disposed atthe second support location and a third rotating assembly is disposed atthe third location.
 14. The gear reducer of claim 11, wherein distancesDA and DC are greater than distance DB.
 15. The gear reducer of claim11, wherein the second location lies outside a triangle defined by thefirst, third and fourth locations.
 16. The gear reducer of claim 11,wherein the distance DA is selected based upon a center distance for asingle stage gear reducer configuration.
 17. The gear reducer of claim11, wherein the distances DB and DC are selected based upon centerdistances for first and second stages of a two stage gear reducerconfiguration.
 18. A gear reducer comprising: a housing comprising apair housing shells having a longitudinal centerline and at least foursupport locations for rotational axes of rotating assemblies, first andsecond support locations being disposed along the centerline and spacedfrom one another by a distance DA, and third and fourth supportlocations being disposed at mirror image locations on either side of thecentral axis, the third and fourth support locations being spaced fromthe first support location by a distance DB and from the second supportlocation by a distance DC; and at least two intermeshing rotatingassemblies, each rotating assembly including a rotational shaft or huband gearing rotational with the shaft or hub, each rotating assemblyhaving a rotational axis coincident with a respective support locationaxis, at least one of the rotating assemblies being disposed at thefirst support location; wherein locations of the supports form aquadrilateral having internal angles less than 180 degrees.
 19. The gearreducer of claim 11, including a first gear reduction stage defined bygearing of rotating assemblies disposed at the first and thirdlocations, and a second gear reduction stage defined by gearing ofrotating assemblies disposed at the second and third locations.
 20. Amethod for making a gear reducer, the method comprising the steps of:providing mating housing shells formed of two identical housing shellblanks for front and rear portions of a housing, the housing blanksincluding first and second rotating assembly supports along a centerlinethereof for supporting rotational members having non-coincidentrotational axes and third and fourth rotating assembly supports at twomirror image locations offset from the centerline; mounting bearing setsin the housing shells at the first supports and at least one of thesecond, third and fourth supports; mounting rotating assemblies withinthe bearing sets; and securing the housing shells to one another. 21.The method of claim 20, wherein the bearing sets and rotating assembliesare mounted at the first and second supports and at one of the third andfourth supports.
 22. The method of claim 20, including the step ofmachining the supports at which the bearing sets are mounted.
 23. Themethod of claim 20, wherein for each shell blank the first support isspaced from the second support by a distance DA, the second support isspaced from the third and fourth supports by a distance DB, and thefirst support is spaced from the third and fourth supports by a distanceDC, and wherein DA and DC are greater than DB.
 24. The method of claim23, wherein the distance DA is selected based upon a center distance fora single stage gear reducer configuration.
 25. The method of claim 23,wherein the distances DB and DC are selected based upon center distancesfor first and second stages of a two stage gear reducer configuration.26. A method for making a gear reducer, the method comprising the stepsof: providing mating housing shells formed of two identical housingshell blanks for front and rear portions of a housing, the housingblanks including first and second rotating assembly supports along acenterline thereof and third and fourth rotating assembly supports attwo mirror image locations offset from the centerline, wherein locationsof the supports form a quadrilateral having internal angles less than180 degrees; mounting bearing sets in the housing shells at the firstsupports and at least one of the second, third and fourth supports;mounting rotating assemblies within the bearing sets; and securing thehousing shells to one another.
 27. A method for making a two stage gearreducer, the method comprising the steps of: providing front and rearidentical housing shells having first and second rotating assemblysupports along a centerline thereof for supporting rotational membershaving non-coincident rotational axes and third and fourth rotatingassembly supports at two mirror image locations offset from thecenterline; machining bearing support surfaces at the first and secondsupports, at the third support of the front housing shell blank, and atthe fourth support of the rear housing shell blank; assembling bearingsand intermeshing rotating assemblies at the machined supports; andsecuring the housing shells to one another to support the bearings androtating assemblies.
 28. The method of claim 27, wherein an inputrotating assembly is supported by the first supports of each shell, anoutput rotating assembly is supported by the second supports of eachshell, and an intermediate rotating assembly is supported by the thirdsupport of the front housing shell and by the fourth support of the rearhousing shell.